let str = new String() //包装类 —— 字符串对象
let s = ''  //字符串字面量

console.log(str);


let n = new Number()
n = 0
console.log(n);



let m = new Boolean()
console.log(m);

let obj = new Object()


let arr = new Array()

let fn = new Function()
let foo=function(){}
console.log(fn);





